Single Pipe Dry Return Rules Check

hboogz

Hey All-

Renovating a basement and would love a confirmation on the height requirements of a single pipe steam system’s dry return. Currently it sits just below the main and runs about 30’ then makes a 90 to a hilTEE then drops down and runs about 15’ to the Hartford loop.

I’m hoping to interrupt the dry return further back , turn it to the far wall, run it high and drop down in the boiler room and put a Tee with Nipples to add much needed venting. Acceptable? Boiler and mains are not being touched to maintain the crucial 28” height requirement.

Just a sanity check on whether I can run the dry return slighter higher than the main?

Attached are some pics

JUGHNE

Think of the dry return as a drain line for the steam main.
The term "dry return" implies that the pipes are drained dry after the system is off and cooled down....this is also how the steam main is considered....drained dry when off/cooled down.

The dry return must move the air out with the steam pushing it thru the pipes to the air vents. Then it could drop down to a wet return.

Any uphill slope of the dry return will keep water in the main and give you water hammer. Also water in the return will keep air from moving out of the main. That is why air vents are on the dry return before it turns into a wet return.
The dry returns must each drop down separately to a wet return If joined together above the wet return the steam from one return/main will close all the air vents. The longer main will not be vented.

hboogz

Thank you for the prompt reply. I believe I have enough clearance to abandon the dry return and convert it to a wet return with proper venting keeping of course 1/8 a foot pitch to the the boiler. Any caveats to that conversion?

Thank you.

Harry.

JUGHNE

Could you explain your question of raising the dry return just a little higher than the main?

A wet return needs no pitch, it is always full of water.
It will stay full to the height of the Hartford nipple at the boiler.
You do not want it to go higher than that HL nipple, IMO.

hboogz

The thought was to run the new dry return on a far wall in parralell to the main but running back to the boiler. But if it’s acting like a drain then it doesn’t make sense that it runs a bit higher(taller) than the main.

I should be able to convert to a wet return pretty easily now that everything is open? Just hav to core drill for a 2.25 pipe

hboogz

Forgot the question mark at the end.

Do you guys feel it’s pretty straight forward to convert this dry return into a wet one ?

Thanks.

Jamie Hall

Yes, provided that you vent the main before it drops down to the wet return. That's essential.

KC_Jones

I would recommend a couple things. One make sure you install provision for cleaning/flushing that wet return. They tend to gunk up, where a dry return won’t. I would suggest doing this at any change of direction with a tee. This is mainly if you go with black pipe. I would also not want to bury the pipe in a wall somewhere just in case it causes problems down the road, but also to access any clean outs.

Another option, use copper as it tends to not gunk up as bad. I know on my system the wet return water looks like drinking water, when it was Steel it looked like chocolate milk all the time.

hboogz

Thank you guys very much. This forum and Dan’s books have been spectacular resources.

I’ll post with pics of the progress. Thinking black pipe from the new hilTEE on the main, then transition to copper for the wet return.

ethicalpaul

And someone correct me if I’m wrong, but you don’t have to worry about pitch on a wet return as long as it it remains below the water line

KC_Jones

ethicalpaul said:

And someone correct me if I’m wrong, but you don’t have to worry about pitch on a wet return as long as it it remains below the water line

Correct, water seeks it's own level so you don't need slope. That said if one was setting it up for maintenance, a little slope wouldn't hurt for flushing purposes. If using copper, probably doesn't matter.

hboogz

Question: since I’m converting to a wet return, I’m coming off the main with a hilTEE straight down then another hilTEE to copper for the wet return. Is it ok to run a 3/4 pipe about 7’ to the closet drain for the new return drain valve. My guess it’s fine so long as it’s closed all the time except when needed to flush.

Yellow is where I’ll add two new steam tees and the direction of wet return. Blue is the proposed run of 3/4 copper to a boiler drain since that’s where I’ll have an accessible drain.

Thoughts?

hboogz

Bumping this for any feedback. Thanks.

Jamie Hall

Should work just fine.

hboogz

Thanks Jaime